usb_pipe_open(9F) Kernel Functions for Drivers usb_pipe_open(9F)NAMEusb_pipe_open - Open a USB pipe to a device
SYNOPSIS
#include <sys/usb/usba.h>
int usb_pipe_open(dev_info_t *dip, usb_ep_descr_t *endpoint,
usb_pipe_policy_t *pipe_policy, usb_flags_t flags, usb_pipe_handle_t
*pipe_handle);
INTERFACE LEVEL
Solaris DDI specific (Solaris DDI)
PARAMETERS
dip
Pointer to the device's dev_info structure.
endpoint
Pointer to endpoint descriptor.
pipe_policy
Pointer to pipe_policy. pipe_policy provides hints on pipe usage.
flags
USB_FLAGS_SLEEP is only flag that is recognized. Wait for memory
resources if not immediately available.
pipe_handle
Address to where new pipe handle is returned. (The
handle is opaque.)
DESCRIPTION
A pipe is a logical connection to an endpoint on a USB device. The
usb_pipe_open() function creates such a logical connection and returns
an initialized handle which refers to that connection.
The USB 2.0 specification defines four endpoint types, each with a cor‐
responding type of pipe. Each of the four types of pipes uses its phys‐
ical connection resource differently. They are:
Control pipe
Used for bursty, non-periodic, reliable, host-initiated
request/response communication, such as for command/status opera‐
tions. These are guaranteed to get approximately 10% of frame time
and will get more if needed and if available, but there is no guar‐
antee on transfer promptness. Bidirectional.
Bulk pipe
Used for large, reliable, non-time-critical data transfers. These
get the bus on a bandwidth-available basis. Unidirectional. Sam‐
ple uses include printer data.
Interrupt pipe
Used for sending or receiving small amounts of reliable data infre‐
quently but with bounded service periods, as for interrupt han‐
dling. Unidirectional.
Isochronous pipe
Used for large, unreliable, time-critical data transfers. Boasts a
guaranteed constant data rate as long as there is data, but there
are no retries of failed transfers. Interrupt and isochronous data
are together guaranteed 90% of frame time as needed. Unidirec‐
tional. Sample uses include audio.
The type of endpoint to which a pipe connects (and therefore the pipe
type) is defined by the bmAttributes field of that pipe's endpoint
descriptor. (See usb_ep_descr(9S)). Opens to interrupt and isochronous
pipes can fail if the required bandwidth cannot be guaranteed.
The polling interval for periodic (interrupt or isochronous) pipes,
carried by the endpoint argument's bInterval field, must be within
range. Valid ranges are:
Full speed: range of 1-255 maps to 1-255 ms.
Low speed: range of 10-255 maps to 10-255 ms.
High speed: range of 1-16 maps to (2**(bInterval-1)) * 125us.
Adequate bandwidth during transfers is guaranteed for all periodic
pipes which are opened successfully. Interrupt and isochronous pipes
have guaranteed latency times, so bandwidth for them is allocated when
they are opened. (Please refer to Sections 5.7 and 5.8 of the USB 2.0
specification which address isochronous and interrupt transfers.) Opens
of interrupt and isochronous pipes fail if inadequate bandwidth is
available to support their guaranteed latency time. Because periodic
pipe bandwidth is allocated on pipe open, open periodic pipes only when
needed.
The bandwidth required by a device varies based on polling interval,
the maximum packet size (wMaxPacketSize) and the device speed. Unallo‐
cated bandwidth remaining for new devices depends on the bandwidth
already allocated for previously opened periodic pipes.
The pipe_policy parameter provides a hint as to pipe usage and must be
specified. It is a usb_pipe_policy_t which contains the following
fields:
uchar_t pp_max_async_reqs:
A hint indicating how many
asynchronous operations requiring
their own kernel thread will be
concurrently in progress, the highest
number of threads ever needed at one
time. Allow at least one for
synchronous callback handling and as
many as are needed to accommodate the
anticipated parallelism of asynchronous*
calls to the following functions:
usb_pipe_close(9F)usb_set_cfg(9F)usb_set_alt_if(9F)usb_clr_feature(9F)usb_pipe_reset(9F)usb_pipe_drain_reqs(9F)usb_pipe_stop_intr_polling(9F)usb_pipe_stop_isoc_polling(9F)
Setting to too small a value can
deadlock the pipe.
* Asynchronous calls are calls made
without the USB_FLAGS_SLEEP flag being
passed. Note that a large number of
callbacks becomes an issue mainly when
blocking functions are called from
callback handlers.
The control pipe to the default endpoints (endpoints for both direc‐
tions with addr 0, sometimes called the default control pipe or default
pipe) comes pre-opened by the hub. A client driver receives the default
control pipe handle through usb_get_dev_data(9F). A client driver can‐
not open the default control pipe manually. Note that the same control
pipe may be shared among several drivers when a device has multiple
interfaces and each interface is operated by its own driver.
All explicit pipe opens are exclusive; attempts to open an opened pipe
fail.
On success, the pipe_handle argument points to an opaque handle of the
opened pipe. On failure, it is set to NULL.
RETURN VALUES
USB_SUCCESS
Open succeeded.
USB_NO_RESOURCES
Insufficient resources were available.
USB_NO_BANDWIDTH
Insufficient bandwidth available. (isochronous and interrupt
pipes).
USB_INVALID_CONTEXT
Called from interrupt handler with USB_FLAGS_SLEEP set.
USB_INVALID_ARGS
dip and/or pipe_handle is NULL. Pipe_policy is NULL.
USB_INVALID_PERM
Endpoint is NULL, signifying the default control pipe. A client
driver cannot open the default control pipe.
USB_NOT_SUPPORTED
Isochronous or interrupt endpoint with maximum packet size of zero
is not supported.
USB_HC_HARDWARE_ERROR
Host controller is in an error state.
USB_FAILURE
Pipe is already open. Host controller not in an operational state.
Polling interval (ep_descr bInterval field) is out of range (intr
or isoc pipes).
CONTEXT
May be called from user or kernel context regardless of arguments. May
also be called from interrupt context if the USB_FLAGS_SLEEP option is
not set.
EXAMPLES
usb_ep_data_t *ep_data;
usb_pipe_policy_t policy;
usb_pipe_handle_t pipe;
usb_client_dev_data_t *reg_data;
uint8_t interface = 1;
uint8_t alternate = 1;
uint8_t first_ep_number = 0;
/* Initialize pipe policy. */
bzero(policy, sizeof(usb_pipe_policy_t));
policy.pp_max_async_requests = 2;
/* Get tree of descriptors for device. */
if (usb_get_dev_data(
dip, USBDRV_VERSION, ®_data, USB_FLAGS_ALL_DESCR, 0) !=
USB_SUCCESS) {
...
}
/* Get first interrupt-IN endpoint. */
ep_data = usb_lookup_ep_data(dip, reg_data, interface, alternate,
first_ep_number, USB_EP_ATTR_INTR, USB_EP_DIR_IN);
if (ep_data == NULL) {
...
}
/* Open the pipe. Get handle to pipe back in 5th argument. */
if (usb_pipe_open(dip, &ep_data.ep_descr
&policy, USB_FLAGS_SLEEP, &pipe) != USB_SUCCESS) {
...
}
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Architecture │PCI-based systems │
├─────────────────────────────┼─────────────────────────────┤
│Interface stability │Evolving │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWusb │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOattributes(5), usb_get_alt_if(9F), usb_get_cfg(9F), usb_get_status(9F),
usb_get_dev_data(9F), usb_pipe_bulk_xfer(9F), usb_pipe_ctrl_xfer(9F),
usb_pipe_close(9F), usb_pipe_get_state(9F), usb_pipe_intr_xfer(9F),
usb_pipe_isoc_xfer(9F), usb_pipe_reset(9F), usb_pipe_set_private(9F),
usb_ep_descr(9S), usb_callback_flags(9S)SunOS 5.10 5 Jan 2004 usb_pipe_open(9F)
